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OpenSim::Millard2012AccelerationMuscle Class Reference

This class implements a 3 state (activation,fiber length and fiber velocity) acceleration musculo-tendon model that has several advantages over equilibrium musculo-tendon models: it is possible to simulate 0 activation, it requires fewer integrator steps to simulate, and physiological active force-length (with a minimum value of 0) and force velocity (with true asymptotes at the maximum shortening and lengthening velocites) curves can be employed. More...

#include <Millard2012AccelerationMuscle.h>

Inheritance diagram for OpenSim::Millard2012AccelerationMuscle:
OpenSim::Muscle OpenSim::PathActuator OpenSim::Actuator OpenSim::Actuator_ OpenSim::Force OpenSim::ModelComponent OpenSim::Object

Classes

struct  AccelerationMuscleInfo

Public Member Functions

 Millard2012AccelerationMuscle ()
 Default constructor: produces a non-functional empty muscle.
 Millard2012AccelerationMuscle (const std::string &aName, double aMaxIsometricForce, double aOptimalFiberLength, double aTendonSlackLength, double aPennationAngle)
 Constructs a functional muscle using all of the default curves and activation model.
double getFiberCompressiveForceLengthMultiplier (SimTK::State &s) const
double getFiberCompressiveForceCosPennationMultiplier (SimTK::State &s) const
double getTendonForceMultiplier (SimTK::State &s) const
double getMass () const
const
MuscleFirstOrderActivationDynamicModel
getActivationModel () const
const
MuscleFixedWidthPennationModel
getPennationModel () const
const ActiveForceLengthCurvegetActiveForceLengthCurve () const
const ForceVelocityCurvegetForceVelocityCurve () const
const FiberForceLengthCurvegetFiberForceLengthCurve () const
const TendonForceLengthCurvegetTendonForceLengthCurve () const
const
FiberCompressiveForceLengthCurve
getFiberCompressiveForceLengthCurve () const
const
FiberCompressiveForceCosPennationCurve
getFiberCompressiveForceCosPennationCurve () const
double getFiberStiffnessAlongTendon (const SimTK::State &s) const
void setActivationModel (MuscleFirstOrderActivationDynamicModel &aActivationMdl)
void setActiveForceLengthCurve (ActiveForceLengthCurve &aActiveForceLengthCurve)
void setForceVelocityCurve (ForceVelocityCurve &aForceVelocityCurve)
void setFiberForceLengthCurve (FiberForceLengthCurve &aFiberForceLengthCurve)
void setTendonForceLengthCurve (TendonForceLengthCurve &aTendonForceLengthCurve)
void setFiberCompressiveForceLengthCurve (FiberCompressiveForceLengthCurve &aFiberCompressiveForceLengthCurve)
void setFiberCompressiveForceCosPennationCurve (FiberCompressiveForceCosPennationCurve &aFiberCompressiveForceCosPennationCurve)
void setMass (double mass)
double getDefaultActivation () const
double getDefaultFiberLength () const
double getDefaultFiberVelocity () const
double getActivationRate (const SimTK::State &s) const
double getFiberVelocity (const SimTK::State &s) const
double getFiberAcceleration (const SimTK::State &s) const
void setDefaultActivation (double activation)
void setDefaultFiberLength (double fiberLength)
void setDefaultFiberVelocity (double fiberVelocity)
void setActivation (SimTK::State &s, double activation) const
void setFiberLength (SimTK::State &s, double fiberLength) const
void setFiberVelocity (SimTK::State &s, double fiberVelocity) const
Array< std::string > getStateVariableNames () const final
SimTK::SystemYIndex getStateVariableSystemIndex (const std::string &stateVariableName) const final
double computeActuation (const SimTK::State &s) const final
void computeInitialFiberEquilibrium (SimTK::State &s) const final
 This function computes the fiber length such that muscle fiber and tendon are developing the same force, and so that the velocity of the entire muscle-tendon is spread between the fiber and the tendon according to their relative compliances.
Property declarations

These are the serializable properties associated with this class.

 OpenSim_DECLARE_PROPERTY (default_activation, double,"assumed initial activation level if none is assigned.")
 OpenSim_DECLARE_PROPERTY (default_fiber_length, double,"assumed initial fiber length if none is assigned.")
 OpenSim_DECLARE_PROPERTY (default_fiber_velocity, double,"assumed initial fiber velocity if none is assigned.")
 OpenSim_DECLARE_UNNAMED_PROPERTY (MuscleFirstOrderActivationDynamicModel,"activation dynamics model with a lower bound")
 OpenSim_DECLARE_UNNAMED_PROPERTY (ActiveForceLengthCurve,"active force length curve")
 OpenSim_DECLARE_UNNAMED_PROPERTY (ForceVelocityCurve,"force velocity curve")
 OpenSim_DECLARE_UNNAMED_PROPERTY (FiberForceLengthCurve,"fiber force length curve")
 OpenSim_DECLARE_UNNAMED_PROPERTY (TendonForceLengthCurve,"Tendon force length curve")
 OpenSim_DECLARE_UNNAMED_PROPERTY (FiberCompressiveForceLengthCurve,"fiber compressive force length curve")
 OpenSim_DECLARE_UNNAMED_PROPERTY (FiberCompressiveForceCosPennationCurve,"fiber compressive force cos(pennationAngle) curve")
 OpenSim_DECLARE_PROPERTY (fiber_damping, double,"fiber damping coefficient")
 OpenSim_DECLARE_PROPERTY (fiber_force_length_damping, double,"fiber force length damping coefficient")
 OpenSim_DECLARE_PROPERTY (fiber_compressive_force_length_damping, double,"fiber compressive force length damping coefficient")
 OpenSim_DECLARE_PROPERTY (fiber_compressive_force_cos_pennation_damping, double,"fiber compressive force cos(pennationAngle) damping coefficient")
 OpenSim_DECLARE_PROPERTY (tendon_force_length_damping, double,"tendon force length damping coefficient")
 OpenSim_DECLARE_PROPERTY (mass, double,"lumped mass")
- Public Member Functions inherited from OpenSim::Muscle
 OpenSim_DECLARE_PROPERTY (max_isometric_force, double,"Maximum isometric force that the fibers can generate")
 OpenSim_DECLARE_PROPERTY (optimal_fiber_length, double,"Optimal length of the muscle fibers")
 OpenSim_DECLARE_PROPERTY (tendon_slack_length, double,"Resting length of the tendon")
 OpenSim_DECLARE_PROPERTY (pennation_angle_at_optimal, double,"Angle between tendon and fibers at optimal fiber length expressed in radians")
 OpenSim_DECLARE_PROPERTY (max_contraction_velocity, double,"Maximum contraction velocity of the fibers, in optimal fiberlengths/second")
 OpenSim_DECLARE_PROPERTY (ignore_tendon_compliance, bool,"Compute muscle dynamics ignoring tendon compliance. Tendon is assumed to be rigid.")
 OpenSim_DECLARE_PROPERTY (ignore_activation_dynamics, bool,"Compute muscle dynamics ignoring activation dynamics. Activation is equivalent to excitation.")
 Muscle ()
 Default constructor.
double getMaxIsometricForce () const
 get/set the maximum isometric force (in N) that the fibers can generate
void setMaxIsometricForce (double maxIsometricForce)
double getOptimalFiberLength () const
 get/set the optimal length (in m) of the muscle fibers (lumped as a single fiber)
void setOptimalFiberLength (double optimalFiberLength)
double getTendonSlackLength () const
 get/set the resting (slack) length (in m) of the tendon that is in series with the muscle fiber
void setTendonSlackLength (double tendonSlackLength)
double getPennationAngleAtOptimalFiberLength () const
 get/set the angle (in radians) between fibers at their optimal fiber length and the tendon
void setPennationAngleAtOptimalFiberLength (double pennationAngle)
double getMaxContractionVelocity () const
 get/set the maximum contraction velocity of the fibers, in optimal fiber-lengths per second
void setMaxContractionVelocity (double maxContractionVelocity)
bool getIgnoreTendonCompliance (const SimTK::State &s) const
 Get/set Modeling (runtime) option to ignore tendon compliance when computing muscle dynamics.
void setIgnoreTendonCompliance (SimTK::State &s, bool ignore) const
bool getIgnoreActivationDynamics (const SimTK::State &s) const
 Get/set Modeling (runtime) option to ignore activation dynamics when computing muscle dynamics.
void setIgnoreActivationDynamics (SimTK::State &s, bool ignore) const
virtual double getActivation (const SimTK::State &s) const
 get the activation level of the muscle, which modulates the active force of the muscle and has a normalized (0 to 1) value Note: method remains virtual to permit override by deprecated muscles.
double getFiberLength (const SimTK::State &s) const
 get the current working fiber length (m) for the muscle
double getPennationAngle (const SimTK::State &s) const
 get the current pennation angle (radians) between the fiber and tendon at the current fiber length
double getCosPennationAngle (const SimTK::State &s) const
 get the cosine of the current pennation angle (radians) between the fiber and tendon at the current fiber length
double getTendonLength (const SimTK::State &s) const
 get the current tendon length (m) given the current joint angles and fiber length
double getNormalizedFiberLength (const SimTK::State &s) const
 get the current normalized fiber length (fiber_length/optimal_fiber_length)
double getFiberLengthAlongTendon (const SimTK::State &s) const
 get the current fiber length (m) projected (*cos(pennationAngle)) onto the tendon direction
double getTendonStrain (const SimTK::State &s) const
 get the current tendon strain (delta_l/tendon_slack_length is dimensionless)
double getFiberPotentialEnergy (const SimTK::State &s) const
 the potential energy (J) stored in the fiber due to its parallel elastic element
double getTendonPotentialEnergy (const SimTK::State &s) const
 the potential energy (J) stored in the tendon
double getMusclePotentialEnergy (const SimTK::State &s) const
 the total potential energy (J) stored in the muscle
double getPassiveForceMultiplier (const SimTK::State &s) const
 get the passive fiber (parallel elastic element) force multiplier
double getActiveForceLengthMultiplier (const SimTK::State &s) const
 get the active fiber (contractile element) force multiplier due to current fiber length
double getNormalizedFiberVelocity (const SimTK::State &s) const
 get normalize fiber velocity (fiber_lengths/s / max_contraction_velocity)
double getFiberVelocityAlongTendon (const SimTK::State &s) const
 get the current afiber velocity (m/s) projected onto the tendon direction
double getPennationAngularVelocity (const SimTK::State &s) const
 get pennation angular velocity (radians/s)
double getTendonVelocity (const SimTK::State &s) const
 get the tendon velocity (m/s) positive is lengthening
double getForceVelocityMultiplier (const SimTK::State &s) const
 get the dimensionless multiplier resulting from the fiber's force-velocity curve
double getFiberForce (const SimTK::State &s) const
 get the current fiber force (N) applied to the tendon
double getFiberForceAlongTendon (const SimTK::State &s) const
 get the force of the fiber (N/m) along the direction of the tendon
double getActiveFiberForce (const SimTK::State &s) const
 get the current active fiber force (N) due to activation*force_length*force_velocity relationships
double getPassiveFiberForce (const SimTK::State &s) const
 get the current passive fiber force (N) passive_force_length relationship
double getActiveFiberForceAlongTendon (const SimTK::State &s) const
 get the current active fiber force (N) projected onto the tendon direction
double getPassiveFiberForceAlongTendon (const SimTK::State &s) const
 get the current passive fiber force (N) projected onto the tendon direction
double getTendonForce (const SimTK::State &s) const
 get the current tendon force (N) applied to bones
double getFiberStiffness (const SimTK::State &s) const
 get the current fiber stiffness (N/m) defined as the partial derivative of fiber force w.r.t.
double getTendonStiffness (const SimTK::State &s) const
 get the current tendon stiffness (N/m) defined as the partial derivative of tendon force w.r.t.
double getMuscleStiffness (const SimTK::State &s) const
 get the current muscle stiffness (N/m) defined as the partial derivative of muscle force w.r.t.
double getFiberActivePower (const SimTK::State &s) const
 get the current active fiber power (W)
double getFiberPassivePower (const SimTK::State &s) const
 get the current passive fiber power (W)
double getTendonPower (const SimTK::State &s) const
 get the current tendon power (W)
double getMusclePower (const SimTK::State &s) const
 get the current muscle power (W)
double getStress (const SimTK::State &s) const
 get the stress in the muscle (part of the Actuator interface as well)
void setExcitation (SimTK::State &s, double excitation) const
 set the excitation (control) for this muscle.
double getExcitation (const SimTK::State &s) const
void equilibrate (SimTK::State &s) const
 Find and set the equilibrium state of the muscle (if any)
- Public Member Functions inherited from OpenSim::PathActuator
 PathActuator ()
GeometryPathupdGeometryPath ()
const GeometryPathgetGeometryPath () const
virtual bool hasGeometryPath () const
 Return a flag indicating whether the Force is applied along a Path.
void setOptimalForce (double aOptimalForce)
double getOptimalForce () const
virtual double getLength (const SimTK::State &s) const
virtual double getLengtheningSpeed (const SimTK::State &s) const
virtual double getPower (const SimTK::State &s) const
void addNewPathPoint (const std::string &proposedName, OpenSim::Body &aBody, const SimTK::Vec3 &aPositionOnBody)
 Note that this function does not maintain the State and so should be used only before a valid State is created.
virtual double computeMomentArm (const SimTK::State &s, Coordinate &aCoord) const
virtual void updateFromXMLNode (SimTK::Xml::Element &aNode, int versionNumber=-1)
 Use this method to deserialize an object from a SimTK::Xml::Element.
virtual void preScale (const SimTK::State &s, const ScaleSet &aScaleSet)
virtual void scale (const SimTK::State &s, const ScaleSet &aScaleSet)
virtual const VisibleObjectgetDisplayer () const
 Methods to support making the object displayable in the GUI or Visualizer Implemented only in few objects.
virtual void updateDisplayer (const SimTK::State &s) const
 In case the ModelComponent has a visual representation (VisualObject), override this method to update it.
 OpenSim_DECLARE_UNNAMED_PROPERTY (GeometryPath,"The set of points defining the path of the muscle.")
 OpenSim_DECLARE_PROPERTY (optimal_force, double,"The maximum force this actuator can produce.")
- Public Member Functions inherited from OpenSim::Actuator
 Actuator ()
virtual double getControl (const SimTK::State &s) const
 Convenience method to set controls given scalar (double) valued control.
virtual int numControls () const
virtual void setForce (const SimTK::State &s, double aForce) const
virtual double getForce (const SimTK::State &s) const
virtual void setSpeed (const SimTK::State &s, double aspeed) const
virtual double getSpeed (const SimTK::State &s) const
void setMinControl (const double &aMinControl)
double getMinControl () const
void setMaxControl (const double &aMaxControl)
double getMaxControl () const
void overrideForce (SimTK::State &s, bool flag) const
 -------------------------------------------------------------------------- Overriding forces -------------------------------------------------------------------------- The force normally produced by an Actuator can be overriden and When the Actuator's force is overriden, the Actuator will by defualt produce a constant force which can be set with setOverrideForce().
bool isForceOverriden (const SimTK::State &s) const
 return Actuator's override status
void setOverrideForce (SimTK::State &s, double value) const
 set the force value used when the override is true
double getOverrideForce (const SimTK::State &s) const
 return override force
 OpenSim_DECLARE_PROPERTY (min_control, double,"Minimum allowed value for control signal. Used primarily when solving ""for control values.")
 Default is -Infinity (no limit).
 OpenSim_DECLARE_PROPERTY (max_control, double,"Maximum allowed value for control signal. Used primarily when solving ""for control values.")
 Default is Infinity (no limit).
- Public Member Functions inherited from OpenSim::Actuator_
 Actuator_ ()
virtual const SimTK::Vector getDefaultControls ()
 Actuator default controls are zero.
virtual const
SimTK::VectorView_< double > 
getControls (const SimTK::State &s) const
virtual void getControls (const SimTK::Vector &modelControls, SimTK::Vector &actuatorControls) const
 Convenience methods for getting, setting and adding to actuator controls from/into the model controls.
virtual void setControls (const SimTK::Vector &actuatorControls, SimTK::Vector &modelControls) const
 set actuator controls subvector into the right slot in the system-wide model controls
virtual void addInControls (const SimTK::Vector &actuatorControls, SimTK::Vector &modelControls) const
 add actuator controls to the values already occupying the slot in the system-wide model controls
virtual void computeEquilibrium (SimTK::State &s) const
- Public Member Functions inherited from OpenSim::Force
 Force (const Force &aForce)
 Implements a copy constructor just so it can invalidate the SimTK::Force index after copying.
Forceoperator= (const Force &aForce)
 Implements a copy assignment operator just so it can invalidate the SimTK::Force index after the assignment.
bool isDisabled (const SimTK::State &s) const
 Return if the Force is disabled or not.
void setDisabled (SimTK::State &s, bool disabled)
 Set the Force as disabled (true) or not (false).
 OpenSim_DECLARE_PROPERTY (isDisabled, bool,"Flag indicating whether the force is disabled or not. Disabled means"" that the force is not active in subsequent dynamics realizations.")
 A Force element is active (enabled) by default.
- Public Member Functions inherited from OpenSim::ModelComponent
 ModelComponent ()
 Default constructor.
 ModelComponent (const std::string &aFileName, bool aUpdateFromXMLNode=true) SWIG_DECLARE_EXCEPTION
 Construct ModelComponent from an XML file.
 ModelComponent (SimTK::Xml::Element &aNode)
 Construct ModelComponent from a specific node in an XML document.
 ModelComponent (const ModelComponent &source)
 Construct ModelComponent with its contents copied from another ModelComponent; this is a deep copy so nothing is shared with the source after the copy.
virtual ~ModelComponent ()
 Destructor is virtual to allow concrete model component cleanup.
ModelComponentoperator= (const ModelComponent &aModelComponent)
 Assignment operator to copy contents of an existing component.
const ModelgetModel () const
 Get a const reference to the Model this component is part of.
ModelupdModel ()
 Get a modifiable reference to the Model this component is part of.
virtual int getNumStateVariables () const
 Get the number of "Continuous" state variables maintained by the ModelComponent and its specified subcomponents.
int getModelingOption (const SimTK::State &state, const std::string &name) const
 Get a ModelingOption flag for this ModelComponent by name.
void setModelingOption (SimTK::State &state, const std::string &name, int flag) const
 Set the value of a ModelingOption flag for this ModelComponent.
double getStateVariable (const SimTK::State &state, const std::string &name) const
 Get the value of a state variable allocated by this ModelComponent.
void setStateVariable (SimTK::State &state, const std::string &name, double value) const
 Set the value of a state variable allocated by this ModelComponent by name.
double getDiscreteVariable (const SimTK::State &state, const std::string &name) const
 Get the value of a discrete variable allocated by this ModelComponent by name.
void setDiscreteVariable (SimTK::State &state, const std::string &name, double value) const
 Set the value of a discrete variable allocated by this ModelComponent by name.
template<typename T >
const T & getCacheVariable (const SimTK::State &state, const std::string &name) const
 Get the value of a cache variable allocated by this ModelComponent by name.
template<typename T >
T & updCacheVariable (const SimTK::State &state, const std::string &name) const
 Obtain a writable cache variable value allocated by this ModelComponent by name.
void markCacheVariableValid (const SimTK::State &state, const std::string &name) const
 After updating a cache variable value allocated by this ModelComponent, you can mark its value as valid, which will not change until the realization stage falls below the minimum set at the time the cache variable was created.
void markCacheVariableInvalid (const SimTK::State &state, const std::string &name) const
 Mark a cache variable value allocated by this ModelComponent as invalid.
bool isCacheVariableValid (const SimTK::State &state, const std::string &name) const
 Enables the to monitor the validity of the cache variable value using the returned flag.
template<typename T >
void setCacheVariable (const SimTK::State &state, const std::string &name, const T &value) const
 Set cache variable value allocated by this ModelComponent by name.
- Public Member Functions inherited from OpenSim::Object
virtual ~Object ()
 Virtual destructor for cleanup.
virtual Objectclone () const =0
 Create a new heap-allocated copy of the concrete object to which this Object refers.
virtual const std::string & getConcreteClassName () const =0
 Returns the class name of the concrete Object-derived class of the actual object referenced by this Object, as a string.
virtual VisibleObjectupdDisplayer ()
 get Non const pointer to VisibleObject
bool isEqualTo (const Object &aObject) const
 Equality operator wrapper for use from languages not supporting operator overloading.
Objectoperator= (const Object &aObject)
 Copy assignment copies he base class fields, including the properties.
virtual bool operator== (const Object &aObject) const
 Determine if two objects are equal.
virtual bool operator< (const Object &aObject) const
 Provide an ordering for objects so they can be put in sorted containers.
void setName (const std::string &name)
 Set the name of the Object.
const std::string & getName () const
 Get the name of this Object.
void setDescription (const std::string &description)
 Set description, a one-liner summary.
const std::string & getDescription () const
 Get description, a one-liner summary.
const std::string & getAuthors () const
 Get Authors of this Object.
void setAuthors (const std::string &authors)
 Set Authors of this object, call this method in your constructor if needed.
const std::string & getReferences () const
 Get references or publications to cite if using this object.
void setReferences (const std::string &references)
 Set references or publications to cite if using this object.
int getNumProperties () const
 Determine how many properties are stored with this Object.
const AbstractPropertygetPropertyByIndex (int propertyIndex) const
 Get a const reference to a property by its index number, returned as an AbstractProperty.
AbstractPropertyupdPropertyByIndex (int propertyIndex)
 Get a writable reference to a property by its index number, returned as an AbstractProperty.
bool hasProperty (const std::string &name) const
 Return true if this Object has a property of any type with the given name, which must not be empty.
const AbstractPropertygetPropertyByName (const std::string &name) const
 Get a const reference to a property by its name, returned as an AbstractProperty.
AbstractPropertyupdPropertyByName (const std::string &name)
 Get a writable reference to a property by its name, returned as an AbstractProperty.
template<class T >
bool hasProperty () const
 Return true if this Object contains an unnamed, one-object property that contains objects of the given template type T.
template<class T >
const Property< T > & getProperty (const PropertyIndex &index) const
 Get property of known type Property<T> as a const reference; the property must be present and have the right type.
template<class T >
Property< T > & updProperty (const PropertyIndex &index)
 Get property of known type Property<T> as a writable reference; the property must be present and have the right type.
void setObjectIsUpToDateWithProperties ()
 When an object is initialized using the current values of its properties, it can set a flag indicating that it is up to date.
bool isObjectUpToDateWithProperties () const
 Returns true if no property's value has changed since the last time setObjectIsUpToDateWithProperties() was called.
void readObjectFromXMLNodeOrFile (SimTK::Xml::Element &objectElement, int versionNumber)
 We're given an XML element from which we are to populate this Object.
virtual void updateXMLNode (SimTK::Xml::Element &parent)
 Serialize this object into the XML node that represents it.
bool getInlined () const
 Inlined means an in-memory Object that is not associated with an XMLDocument.
void setInlined (bool aInlined, const std::string &aFileName="")
 Mark this as inlined or not and optionally provide a file name to associate with the new XMLDocument for the non-inline case.
std::string getDocumentFileName () const
 If there is a document associated with this object then return the file name maintained by the document.
void setAllPropertiesUseDefault (bool aUseDefault)
bool print (const std::string &fileName)
 Write this Object into an XML file of the given name; conventionally the suffix to use is ".osim".
std::string dump (bool dumpName=false)
 dump the XML representation of this Object into an std::string and return it.
void clearObjectIsUpToDateWithProperties ()
 For testing or debugging purposes, manually clear the "object is up to date with respect to properties" flag.
virtual bool isA (const char *type) const
 The default implementation returns true only if the supplied string is "Object"; each Object-derived class overrides this to match its own class name.
const std::string & toString () const
 Wrapper to be used on Java side to display objects in tree; this returns just the object's name.
PropertySetgetPropertySet ()
 OBSOLETE: Get a reference to the PropertySet maintained by the Object.
const PropertySetgetPropertySet () const

Protected Member Functions

void postScale (const SimTK::State &s, const ScaleSet &aScaleSet)
 Related to scaling, soon to be removed.
double calcActivationRate (const SimTK::State &s) const
void calcMuscleLengthInfo (const SimTK::State &s, MuscleLengthInfo &mli) const final
 calculate muscle's position related values such fiber and tendon lengths, normalized lengths, pennation angle, etc...
virtual void calcFiberVelocityInfo (const SimTK::State &s, FiberVelocityInfo &fvi) const final
 calculate muscle's velocity related values such fiber and tendon velocities,normalized velocities, pennation angular velocity, etc...
void calcMuscleDynamicsInfo (const SimTK::State &s, MuscleDynamicsInfo &mdi) const final
 calculate muscle's active and passive force-length, force-velocity, tendon force, relationships and their related values
void calcMusclePotentialEnergyInfo (const SimTK::State &s, MusclePotentialEnergyInfo &mpei) const final
 calculate muscle's fiber and tendon potential energy
void connectToModel (Model &model) final
 Sets up the ModelComponent from the model, if necessary.
void addToSystem (SimTK::MultibodySystem &system) const final
 Creates the ModelComponent so that it can be used in simulation.
void initStateFromProperties (SimTK::State &s) const final
 Initializes the state of the ModelComponent.
void setPropertiesFromState (const SimTK::State &s) final
 Sets the default state for ModelComponent.
SimTK::Vector computeStateVariableDerivatives (const SimTK::State &s) const final
 computes state variable derivatives
void setStateVariableDeriv (const SimTK::State &s, const std::string &aStateName, double aValue) const
 Set the derivative of an actuator state, specified by name.
double getStateVariableDeriv (const SimTK::State &s, const std::string &aStateName) const
 Get the derivative of an actuator state, by index.
- Protected Member Functions inherited from OpenSim::Muscle
const MuscleLengthInfogetMuscleLengthInfo (const SimTK::State &s) const
 Developer Access to intermediate values calculate by the muscle model.
MuscleLengthInfoupdMuscleLengthInfo (const SimTK::State &s) const
const FiberVelocityInfogetFiberVelocityInfo (const SimTK::State &s) const
FiberVelocityInfoupdFiberVelocityInfo (const SimTK::State &s) const
const MuscleDynamicsInfogetMuscleDynamicsInfo (const SimTK::State &s) const
MuscleDynamicsInfoupdMuscleDynamicsInfo (const SimTK::State &s) const
const MusclePotentialEnergyInfogetMusclePotentialEnergyInfo (const SimTK::State &s) const
MusclePotentialEnergyInfoupdMusclePotentialEnergyInfo (const SimTK::State &s) const
virtual void computeFiberEquilibriumAtZeroVelocity (SimTK::State &s) const
 Provide a quick estimate of the fiber length assuming the musculotendon unit velocity is zero.
void computeForce (const SimTK::State &state, SimTK::Vector_< SimTK::SpatialVec > &bodyForces, SimTK::Vector &generalizedForce) const override
 Force interface applies tension to bodies, and Muscle also checks that applied muscle tension is not negative.
double computePotentialEnergy (const SimTK::State &state) const override
 Potential energy stored by the muscle.
SimTK::Vec3 computePathColor (const SimTK::State &state) const override
 Override PathActuator virtual to calculate a preferred color for the muscle path based on activation.
virtual void updateGeometry (const SimTK::State &s)
- Protected Member Functions inherited from OpenSim::PathActuator
void realizeDynamics (const SimTK::State &state) const override
 Extension of parent class method; derived classes may extend further.
- Protected Member Functions inherited from OpenSim::Actuator
double computeOverrideForce (const SimTK::State &s) const
OpenSim::Array< std::string > getRecordLabels () const
 Methods to query a Force for the value actually applied during simulation The names of the quantities (column labels) is returned by this first function getRecordLabels()
OpenSim::Array< double > getRecordValues (const SimTK::State &state) const
 Given SimTK::State object extract all the values necessary to report forces, application location frame, etc.
- Protected Member Functions inherited from OpenSim::Actuator_
virtual void updateGeometry ()
- Protected Member Functions inherited from OpenSim::Force
 Force ()
 Default constructor sets up Force-level properties; can only be called from a derived class constructor.
 Force (SimTK::Xml::Element &node)
 Deserialization from XML, necessary so that derived classes can (de)serialize.
void applyForceToPoint (const SimTK::State &state, const OpenSim::Body &body, const SimTK::Vec3 &point, const SimTK::Vec3 &force, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
 Apply a force at a particular point (a "station") on a given body.
void applyTorque (const SimTK::State &state, const OpenSim::Body &body, const SimTK::Vec3 &torque, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
 Apply a torque to a particular body.
void applyGeneralizedForce (const SimTK::State &state, const Coordinate &coord, double force, SimTK::Vector &generalizedForces) const
 Apply a generalized force.
- Protected Member Functions inherited from OpenSim::ModelComponent
virtual void generateDecorations (bool fixed, const ModelDisplayHints &hints, const SimTK::State &state, SimTK::Array_< SimTK::DecorativeGeometry > &appendToThis) const
 Optional method for generating arbitrary display geometry that reflects this ModelComponent at the specified state.
virtual void realizeTopology (SimTK::State &state) const
 Obtain state resources that are needed unconditionally, and perform computations that depend only on the system topology.
virtual void realizeModel (SimTK::State &state) const
 Obtain state resources that may be needed, depending on modeling options, and perform computations that depend only on topology and selected modeling options.
virtual void realizeInstance (const SimTK::State &state) const
 Perform computations that depend only on instance variables, like lengths and masses.
virtual void realizeTime (const SimTK::State &state) const
 Perform computations that depend only on time and earlier stages.
virtual void realizePosition (const SimTK::State &state) const
 Perform computations that depend only on position-level state variables and computations performed in earlier stages (including time).
virtual void realizeVelocity (const SimTK::State &state) const
 Perform computations that depend only on velocity-level state variables and computations performed in earlier stages (including position, and time).
virtual void realizeAcceleration (const SimTK::State &state) const
 Perform computations that may depend on applied forces.
virtual void realizeReport (const SimTK::State &state) const
 Perform computations that may depend on anything but are only used for reporting and cannot affect subsequent simulation behavior.
void includeAsSubComponent (ModelComponent *aComponent)
 Include another ModelComponent as a Subcomponent of this ModelComponent.
void addModelingOption (const std::string &optionName, int maxFlagValue) const
 Add a modeling option (integer flag stored in the State) for use by this ModelComponent.
void addStateVariable (const std::string &stateVariableName, SimTK::Stage invalidatesStage=SimTK::Stage::Dynamics) const
 Add a continuous system state variable belonging to this ModelComponent, and assign a name by which to refer to it.
void addDiscreteVariable (const std::string &discreteVariableName, SimTK::Stage invalidatesStage) const
 Add a system discrete variable belonging to this ModelComponent, give it a name by which it can be referenced, and declare the lowest Stage that should be invalidated if this variable's value is changed.
template<class T >
void addCacheVariable (const std::string &cacheVariableName, const T &variablePrototype, SimTK::Stage dependsOnStage) const
 Add a state cache entry belonging to this ModelComponent to hold calculated values that must be automatically invalidated when certain state values change.
const int getStateIndex (const std::string &name) const
 Get the index of a ModelComponent's continuous state variable in the Subsystem for allocations.
const SimTK::DiscreteVariableIndex getDiscreteVariableIndex (const std::string &name) const
 Get the index of a ModelComponent's discrete variable in the Subsystem for allocations.
const SimTK::CacheEntryIndex getCacheVariableIndex (const std::string &name) const
 Get the index of a ModelComponent's cache variable in the Subsystem for allocations.
- Protected Member Functions inherited from OpenSim::Object
 Object ()
 The default constructor is only for use by constructors of derived types.
 Object (const std::string &fileName, bool aUpdateFromXMLNode=true) SWIG_DECLARE_EXCEPTION
 Constructor from a file, to be called from other constructors that take a file as input.
 Object (const Object &source)
 Copy constructor is invoked automatically by derived classes with default copy constructors; otherwise it must be invoked explicitly.
 Object (SimTK::Xml::Element &aElement)
 Construct the base class portion of an Object from a given Xml element that describes this Object.
template<class T >
PropertyIndex addProperty (const std::string &name, const std::string &comment, const T &value)
 Define a new single-value property of known type T, with the given name, associated comment, and initial value.
template<class T >
PropertyIndex addOptionalProperty (const std::string &name, const std::string &comment)
 Add an optional property, meaning it can contain either no value or a single value.
template<class T >
PropertyIndex addOptionalProperty (const std::string &name, const std::string &comment, const T &value)
 Add an optional property, meaning it can contain either no value or a single value.
template<class T >
PropertyIndex addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize)
 Define a new list-valued property of known type T, with the given name, associated comment, minimum (==0) and maximum (>0) allowable list lengths, and a zero-length initial value.
template<class T , template< class > class Container>
PropertyIndex addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize, const Container< T > &valueList)
 Define a new list-valued property as above, but assigning an initial value via some templatized container class that supports size() and indexing.
PropertyIndex getPropertyIndex (const std::string &name) const
 Look up a property by name and return its PropertyIndex if it is found.
template<class T >
PropertyIndex getPropertyIndex () const
 Look up an unnamed property by the type of object it contains, and return its PropertyIndex if it is found.
void updateFromXMLDocument ()
 Use this method only if you're deserializing from a file and the object is at the top level; that is, primarily in constructors that take a file name as input.
void setDocument (XMLDocument *doc)
 Unconditionally set the XMLDocument associated with this object.
const XMLDocumentgetDocument () const
 Get a const pointer to the document (if any) associated with this object.
XMLDocumentupdDocument ()
 Get a writable pointer to the document (if any) associated with this object.

Additional Inherited Members

- Static Public Member Functions inherited from OpenSim::Object
static void registerType (const Object &defaultObject)
 Register an instance of a class; if the class is already registered it will be replaced.
static void renameType (const std::string &oldTypeName, const std::string &newTypeName)
 Support versioning by associating the current Object type with an old name.
static const ObjectgetDefaultInstanceOfType (const std::string &concreteClassName)
 Return a pointer to the default instance of the registered (concrete) Object whose class name is given, or NULL if the type is not registered.
template<class T >
static bool isObjectTypeDerivedFrom (const std::string &concreteClassName)
 Return true if the given concrete object type represents a subclass of the template object type T, and thus could be referenced with a T*.
static ObjectnewInstanceOfType (const std::string &concreteClassName)
 Create a new instance of the concrete Object type whose class name is given as concreteClassName.
static void getRegisteredTypenames (Array< std::string > &typeNames)
 Retrieve all the typenames registered so far.
template<class T >
static void getRegisteredObjectsOfGivenType (ArrayPtrs< T > &rArray)
 Return an array of pointers to the default instances of all registered (concrete) Object types that derive from a given Object-derived type that does not have to be concrete.
static void PrintPropertyInfo (std::ostream &os, const std::string &classNameDotPropertyName)
 Dump formatted property information to a given output stream, useful for creating a "help" facility for registered objects.
static void PrintPropertyInfo (std::ostream &os, const std::string &className, const std::string &propertyName)
 Same as the other signature but the class name and property name are provided as two separate strings.
static ObjectmakeObjectFromFile (const std::string &fileName)
 Create an OpenSim object whose type is based on the tag at the root node of the XML file passed in.
static const std::string & getClassName ()
 Return the name of this class as a string; i.e., "Object".
static void setSerializeAllDefaults (bool shouldSerializeDefaults)
 Static function to control whether all registered objects and their properties are written to the defaults section of output files rather than only those values for which the default was explicitly overwritten when read in from an input file or set programmatically.
static bool getSerializeAllDefaults ()
 Report the value of the "serialize all defaults" flag.
static bool isKindOf (const char *type)
 Returns true if the passed-in string is "Object"; each Object-derived class defines a method of this name for its own class name.
static void setDebugLevel (int newLevel)
 Set the debug level to get verbose output.
static int getDebugLevel ()
 Get current setting of debug level.
static ObjectSafeCopy (const Object *aObject)
 Use the clone() method to duplicate the given object unless the pointer is null in which case null is returned.
static void RegisterType (const Object &defaultObject)
 OBSOLETE alternate name for registerType().
static void RenameType (const std::string &oldName, const std::string &newName)
 OBSOLETE alternate name for renameType().
- Static Public Attributes inherited from OpenSim::Object
static const std::string DEFAULT_NAME
 Name used for default objects when they are serialized.
- Protected Attributes inherited from OpenSim::Muscle
double _muscleWidth
 The assumed fixed muscle-width from which the fiber pennation angle can be calculated.
double _maxIsometricForce
 to support deprecated muscles
double _optimalFiberLength
double _pennationAngleAtOptimal
double _tendonSlackLength

Detailed Description

This class implements a 3 state (activation,fiber length and fiber velocity) acceleration musculo-tendon model that has several advantages over equilibrium musculo-tendon models: it is possible to simulate 0 activation, it requires fewer integrator steps to simulate, and physiological active force-length (with a minimum value of 0) and force velocity (with true asymptotes at the maximum shortening and lengthening velocites) curves can be employed.

fig_Millard2012AccelerationMuscle.png

The dynamic equation of the mass, constrained to move in direction $ \hat{i} $ is given by the scalar equation:

\[ m \ddot{x} = F_{SE} - F_{CE} \cdot \hat{i} \]

The kinematic expression for the acceleration of the mass, $ \ddot{s} $, expressed in terms of the fiber length, $l_{CE}$, and pennation angle $\phi$ is

\[ \ddot{x} = \Big(\ddot{l}_{CE} \cos \phi - 2 \dot{l}_{CE}\dot{\phi}\sin\phi - \dot{\phi}^2 l_{CE} \cos \phi - \ddot{\phi} l_{CE} \sin \phi\Big) \]

The kinematic expression for the angular acceleration of the pennation angle can be found by taking the second derivative of the pennation constraint equation

\[ l_{CE} \sin \phi = h \]

which yields

\[ \ddot{\phi} = -\Big( \ddot{l}_{CE}\sin\phi + 2 \dot{l}_{CE} \dot{\phi} \cos\phi - \dot{\phi}^2 l_{CE} \sin \phi \Big) / \Big( l_{CE} \cos \phi \Big) \]

An expression for $ \ddot{l}_{CE}$ can be obtained by substituting in the equations $ \ddot{\phi} $ into the equation for $\ddot{x}$ and simplifying:

\[ \ddot{l}_{CE} = \frac{1}{m} \Big( F_{SE} - F_{CE} \cdot \hat{i} \Big) \cos \phi + l_{CE} \dot{\phi}^2 \]

Notice that the above equation for $\ddot{l}_{CE}$ has no singularities, provided that there are no singularities in $ F_{SE}$ and $ F_{M}\cdot\hat{i}$. The force the fiber applies to the tendon (in N), $F_{CE}\cdot\hat{i}$, is given by (+'ve is tension)

\[ F_{CE} \cdot \hat{i} = f_{ISO}\Big(\mathbf{a} \mathbf{f}_L(\hat{l}_{CE}) \mathbf{f}_V(\frac{\hat{v}_{CE}}{v_{MAX}}) + \beta_{CE}\hat{v}_{CE} + \mathbf{f}_{PE}(\hat{l}_{CE})(1+\beta_{PE}\hat{v}_{CE}) - \mathbf{f}_K(\hat{l}_{CE})(1-\beta_{K}\hat{v}_{CE}) \Big) \cos \phi - f_{ISO} \Big( \mathbf{f}_{c\phi}(\cos \phi) (1- \beta_{c \phi} \frac{d}{dt}(\frac{l_{CE}\cos\phi}{l_{CE,OPT}\cos\phi_{OPT}})) \Big) \]

The force the tendon generates (in N) is given by (+'ve is tension)

\[ F_{SE} = f_{ISO} \mathbf{f}_{SE}(\hat{l}_{SE})(1+\beta_{SE}\hat{v}_{SE}) \]

Every elastic element ( $\mathbf{f}_{PE}$, $\mathbf{f}_{K}$, $\mathbf{f}_{c\phi}$, and $\mathbf{f}_{SE}$) is accompanied by a non-linear damping element of a form that is identical to the damping found in a Hunt-Crossley contact model. Additionally a linear damping element, $\beta_{CE}\hat{v}_{CE}$, is located in the fiber as in J.He et al. Damping is necessary to include in this model to prevent the mass from oscillating in a non-physiologic manner. Nonlinear damping Hunt-Crossley damping (where the damping force is scaled by the elastic force) has been chosen because this form of damping doesn't increase the stiffness of the system equations (because it is gradually turned on).

As with the Hunt-Crossley contact model, the force generated by the nonlinear spring and damper saturated so that it is greater than or equal to zero. This saturation is necessary to ensure that tension elements can only generate tensile forces, and that compressive elements only generate compressive forces. Note that the sign conventions have been chosen so that damping forces are generated in the correct direction for each element.

\begin{eqnarray*} (1+\beta_{PE}\hat{v}_{CE}) > 0 \\ (1-\beta_{K}\hat{v}_{CE}) > 0 \\ (1- \beta_{c \phi} \frac{d}{dt}(\frac{l_{CE}\cos\phi}{l_{CE,OPT}\cos\phi_{OPT}})) > 0 \\ (1+\beta_{SE}\hat{v}_{SE}) > 0 \end{eqnarray*}

For more information on these new terms please see the doxygen for FiberCompressiveForceLengthCurve, FiberCompressiveForceCosPennationCurve, and MuscleFirstOrderActivationDynamicModel.

Units

  • m: meters
  • rad: radians
  • N: Newtons
  • kg: kilograms
  • s: seconds

Usage

Note that this object should be updated through the set methods provided. These set methods will take care of rebuilding the muscle correctly. If you modify the properties directly, the curve will not be rebuilt, and upon calling a function that requires a state an exception will be thrown because the muscle is out of date with its properties.

Note that this muscle does not currently implement the ignore_tendon_compliance flag, nor the ignore_activation_dynamics flag.

Nomenclature

Note that dot notation is used to denote time derivatives (units of $m/s$ and $m/s^2$ in this case), where as the hat symbol (as in $\hat{l}$, $\hat{v}$) is used to denote time derivatives that have been scaled by a characteristic dimension (appear in units of $1/s$ and $1/s^2$ in this case)

  • $m$: is the mass located at the junction between the fiber and the tendon. This mass should be thought of as a time constant that indicates how quickly this model will converge to the force an equilibrium muscle-tendon model would produce ( $kg$)
  • $\ddot{x}$: is the acceleration of the mass, in the $\hat{i}$ direction ( $m/s^2$)
  • $F_{SE}$: is the force developed by the tendon ( $N$)
  • $F_{CE}\cdot\hat{i}$: is the force developed by the fiber along the tendon ( $N$)
  • $l_{CE}$: Length of the fiber(m)
  • $l_{CE,OPT}$: Length the fiber generates maximal isometric force (m)
  • $\hat{l}_{CE}=l_{CE}/l_{CE,OPT}$: Normalized length of the fiber (dimensionless)
  • $\hat{v}_{CE}=\dot{l}_{CE}/l_{CE,OPT}$: Fiber velocity divided by ( $1/s$)
  • $\hat{v}_{MAX}$: Maximum normalized fiber velocity ( $l_{CE,OPT}/s$). This quantity typically ranges between 10 and 15 lengths per second (1/s)
  • $\phi$: Pennation angle(rad)
  • $\phi_{OPT}$: Pennation angle when the fiber is at its optimal length (rad)
  • $l_{SE}$: Length of the series element (tendon) (m)
  • $l_{SE,R}$: Resting length of the series element(m)
  • $\hat{l}_{SE} = l_{SE}/l_{SE,R}$: Normalized length of the series element (dimensionless)
  • $ \hat{v}_{SE} = \dot{l}_{SE}/l_{SE,R}$: Normalized velocity of the tendon (1/s)
  • $f_{ISO}$: maximum force the muscle can develop statically ( $\hat{v}_{CE}=0$) at its optimal length ( $l_{CE,OPT}$) and pennation angle ( $\phi_{OPT}$)
  • $\mathbf{a}$: activation (unitless)
  • $\mathbf{f}_L(\hat{l}_{CE})$: Active force length multiplier (dimensionless)
  • $\mathbf{f}_V(\frac{\hat{v}_{CE}}{v_{MAX}})$: Force velocity multiplier (dimensionless)
  • $\mathbf{f}_{PE}(\hat{l}_{CE})$: Passive force length multiplier (dimensionless)
  • $\mathbf{f}_{K}(\hat{l}_{CE})$: Fiber compressive force length multiplier (dimensionless)
  • $\mathbf{f}_{c\phi}(\cos \phi)$: Fiber compressive cosine pennation multiplier (dimensionless)
  • $\mathbf{f}_{SE}(\hat{l}_{SE})$: Series element (tendon) force-length multiplier (dimensionless)
  • $\beta_{CE}$: Fiber damping (s)
  • $\beta_{PE}$: Fiber parallel element damping coefficient (s)
  • $\beta_{K}$: Fiber compressive force length damping coefficient (s)
  • $\beta_{c \phi}$: Fiber compressive cosine pennation damping coefficient (s)
  • $\beta_{SE}$: Series element (tendon) force length damping coefficient (s)

References

Hunt,K., and Crossley,F. Coecient of restitution interpreted as damping in v ibroimpact. Transactions of the ASME Journal of Applied Mechanics, 42(E):440445, 1975.

J.He, W.S. Levine, and G.E. Leob."The Modelling of the Neuro-musculo-skeletal Control System of A Cat Hindlimb", Proceedings of the IEEE International Symposium on Intelligent Control, 1988.

Author
Matt Millard

Constructor & Destructor Documentation

OpenSim::Millard2012AccelerationMuscle::Millard2012AccelerationMuscle ( )

Default constructor: produces a non-functional empty muscle.

OpenSim::Millard2012AccelerationMuscle::Millard2012AccelerationMuscle ( const std::string &  aName,
double  aMaxIsometricForce,
double  aOptimalFiberLength,
double  aTendonSlackLength,
double  aPennationAngle 
)

Constructs a functional muscle using all of the default curves and activation model.

Parameters
aNameThe name of the muscle.
aMaxIsometricForceThe force generated by the muscle when it at its optimal resting length, has a contraction velocity of zero, and is fully activated (Newtons).
aOptimalFiberLengthThe optimal length of the muscle fiber (meters).
aTendonSlackLengthThe resting length of the tendon (meters).
aPennationAngleThe angle of the fiber relative to the tendon when the fiber is at its optimal resting length (radians).

Member Function Documentation

void OpenSim::Millard2012AccelerationMuscle::addToSystem ( SimTK::MultibodySystem &  system) const
protectedvirtual

Creates the ModelComponent so that it can be used in simulation.

Parameters
systemthe multibody system

Reimplemented from OpenSim::Muscle.

double OpenSim::Millard2012AccelerationMuscle::calcActivationRate ( const SimTK::State &  s) const
protected
Parameters
sthe state of the model
Returns
the time derivative of activation
virtual void OpenSim::Millard2012AccelerationMuscle::calcFiberVelocityInfo ( const SimTK::State &  s,
FiberVelocityInfo fvi 
) const
protectedvirtual

calculate muscle's velocity related values such fiber and tendon velocities,normalized velocities, pennation angular velocity, etc...

Parameters
sthe state of the model
fvithe fiber velocity info struct that will hold updated information about the muscle that is available at the velocity stage

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::calcMuscleDynamicsInfo ( const SimTK::State &  s,
MuscleDynamicsInfo mdi 
) const
protectedvirtual

calculate muscle's active and passive force-length, force-velocity, tendon force, relationships and their related values

Parameters
sthe state of the model
mdithe muscle dynamics info struct that will hold updated information about the muscle that is available at the dynamics stage

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::calcMuscleLengthInfo ( const SimTK::State &  s,
MuscleLengthInfo mli 
) const
protectedvirtual

calculate muscle's position related values such fiber and tendon lengths, normalized lengths, pennation angle, etc...

Parameters
sthe state of the model
mlithe muscle length info struct that will hold updated information about the muscle that is available at the position stage

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::calcMusclePotentialEnergyInfo ( const SimTK::State &  s,
MusclePotentialEnergyInfo mpei 
) const
protectedvirtual

calculate muscle's fiber and tendon potential energy

Reimplemented from OpenSim::Muscle.

double OpenSim::Millard2012AccelerationMuscle::computeActuation ( const SimTK::State &  s) const
virtual
Parameters
sthe state of the system
Returns
the tensile force the muscle is generating in N

Implements OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::computeInitialFiberEquilibrium ( SimTK::State &  s) const
virtual

This function computes the fiber length such that muscle fiber and tendon are developing the same force, and so that the velocity of the entire muscle-tendon is spread between the fiber and the tendon according to their relative compliances.

Parameters
sthe state of the system

Implements OpenSim::Muscle.

SimTK::Vector OpenSim::Millard2012AccelerationMuscle::computeStateVariableDerivatives ( const SimTK::State &  s) const
protectedvirtual

computes state variable derivatives

Parameters
sthe state of the model

Reimplemented from OpenSim::ModelComponent.

void OpenSim::Millard2012AccelerationMuscle::connectToModel ( Model model)
protectedvirtual

Sets up the ModelComponent from the model, if necessary.

Parameters
modelthe dynamic model

Reimplemented from OpenSim::Muscle.

const MuscleFirstOrderActivationDynamicModel& OpenSim::Millard2012AccelerationMuscle::getActivationModel ( ) const
Returns
the MuscleFirstOrderActivationDynamicModel that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getActivationRate ( const SimTK::State &  s) const
Parameters
sThe state of the system
Returns
the time derivative of activation
const ActiveForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getActiveForceLengthCurve ( ) const
Returns
the ActiveForceLengthCurve that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getDefaultActivation ( ) const
Returns
the default activation level that is used as an initial condition if none is provided by the user.
double OpenSim::Millard2012AccelerationMuscle::getDefaultFiberLength ( ) const
Returns
the default fiber length that is used as an initial condition if none is provided by the user.
double OpenSim::Millard2012AccelerationMuscle::getDefaultFiberVelocity ( ) const
Returns
the default fiber velocity that is used as an initial condition if none is provided by the user.
double OpenSim::Millard2012AccelerationMuscle::getFiberAcceleration ( const SimTK::State &  s) const
Parameters
sThe state of the system
Returns
the acceleration of the fiber (m/s)
const FiberCompressiveForceCosPennationCurve& OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceCosPennationCurve ( ) const
Returns
the FiberCompressiveForceCosPennationCurve that this muscle model uses.
double OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceCosPennationMultiplier ( SimTK::State &  s) const
Parameters
sthe state of the system
Returns
the normalized force term associated with the compressive force cosine pennation element, $\mathbf{f}_{c\phi}(\cos \phi)$, in the equilibrium equation
const FiberCompressiveForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceLengthCurve ( ) const
Returns
the FiberCompressiveForceLengthCurve that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceLengthMultiplier ( SimTK::State &  s) const
Parameters
sthe state of the system
Returns
the normalized force term associated with the compressive force length element, $\mathbf{f}_K(\hat{l}_{CE})$, in the equilibrium equation
const FiberForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getFiberForceLengthCurve ( ) const
Returns
the FiberForceLengthCurve that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getFiberStiffnessAlongTendon ( const SimTK::State &  s) const
Returns
the stiffness of the muscle fibers along the tendon (N/m)

Reimplemented from OpenSim::Muscle.

double OpenSim::Millard2012AccelerationMuscle::getFiberVelocity ( const SimTK::State &  s) const
Parameters
sThe state of the system
Returns
the velocity of the fiber (m/s)

Reimplemented from OpenSim::Muscle.

const ForceVelocityCurve& OpenSim::Millard2012AccelerationMuscle::getForceVelocityCurve ( ) const
Returns
the ForceVelocityInverseCurve that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getMass ( ) const
Returns
the size of the mass between the tendon and fiber
const MuscleFixedWidthPennationModel& OpenSim::Millard2012AccelerationMuscle::getPennationModel ( ) const
Returns
the MuscleFixedWidthPennationModel that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getStateVariableDeriv ( const SimTK::State &  s,
const std::string &  aStateName 
) const
protected

Get the derivative of an actuator state, by index.

Parameters
sthe state
aStateNamethe name of the state to get.
Returns
The value of the state derivative
Array<std::string> OpenSim::Millard2012AccelerationMuscle::getStateVariableNames ( ) const
virtual
Returns
A string arraw of the state variable names

Reimplemented from OpenSim::ModelComponent.

SimTK::SystemYIndex OpenSim::Millard2012AccelerationMuscle::getStateVariableSystemIndex ( const std::string &  stateVariableName) const
virtual
Parameters
stateVariableNamethe name of the state varaible in question
Returns
The system index of the state variable in question

Reimplemented from OpenSim::ModelComponent.

const TendonForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getTendonForceLengthCurve ( ) const
Returns
the TendonForceLengthCurve that this muscle model uses
double OpenSim::Millard2012AccelerationMuscle::getTendonForceMultiplier ( SimTK::State &  s) const
Parameters
sthe state of the system
Returns
the normalized force term associated with tendon element, $\mathbf{f}_{SE}(\hat{l}_{T})$, in the equilibrium equation
void OpenSim::Millard2012AccelerationMuscle::initStateFromProperties ( SimTK::State &  s) const
protectedvirtual

Initializes the state of the ModelComponent.

Parameters
sthe state of the model

Reimplemented from OpenSim::Muscle.

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( default_activation  ,
double  ,
"assumed initial activation level if none is assigned."   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( default_fiber_length  ,
double  ,
"assumed initial fiber length if none is assigned."   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( default_fiber_velocity  ,
double  ,
"assumed initial fiber velocity if none is assigned."   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( fiber_damping  ,
double  ,
"fiber damping coefficient"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( fiber_force_length_damping  ,
double  ,
"fiber force length damping coefficient"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( fiber_compressive_force_length_damping  ,
double  ,
"fiber compressive force length damping coefficient"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( fiber_compressive_force_cos_pennation_damping  ,
double  ,
"fiber compressive force cos(pennationAngle) damping coefficient"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( tendon_force_length_damping  ,
double  ,
"tendon force length damping coefficient"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY ( mass  ,
double  ,
"lumped mass"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( MuscleFirstOrderActivationDynamicModel  ,
"activation dynamics model with a lower bound"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( ActiveForceLengthCurve  ,
"active force length curve"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( ForceVelocityCurve  ,
"force velocity curve"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( FiberForceLengthCurve  ,
"fiber force length curve"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( TendonForceLengthCurve  ,
"Tendon force length curve"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( FiberCompressiveForceLengthCurve  ,
"fiber compressive force length curve"   
)
OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY ( FiberCompressiveForceCosPennationCurve  ,
"fiber compressive force cos(pennationAngle) curve"   
)
void OpenSim::Millard2012AccelerationMuscle::postScale ( const SimTK::State &  s,
const ScaleSet aScaleSet 
)
protectedvirtual

Related to scaling, soon to be removed.

Parameters
sthe state of the model
aScaleSetthe scale set

Reimplemented from OpenSim::PathActuator.

void OpenSim::Millard2012AccelerationMuscle::setActivation ( SimTK::State &  s,
double  activation 
) const
virtual
Parameters
sthe state of the system
activationthe desired activation level

Implements OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::setActivationModel ( MuscleFirstOrderActivationDynamicModel aActivationMdl)
Parameters
aActivationMdlthe MuscleFirstOrderActivationDynamicModel that this muscle model uses to simulate activation dynamics
void OpenSim::Millard2012AccelerationMuscle::setActiveForceLengthCurve ( ActiveForceLengthCurve aActiveForceLengthCurve)
Parameters
aActiveForceLengthCurvethe ActiveForceLengthCurve that this muscle model uses to scale active fiber force as a function of length
void OpenSim::Millard2012AccelerationMuscle::setDefaultActivation ( double  activation)
Parameters
activationthe default activation level that is used to initialize the muscle
void OpenSim::Millard2012AccelerationMuscle::setDefaultFiberLength ( double  fiberLength)
Parameters
fiberLengththe default fiber length that is used to initialize the muscle
void OpenSim::Millard2012AccelerationMuscle::setDefaultFiberVelocity ( double  fiberVelocity)
Parameters
fiberVelocitythe default fiber velocity that is used to initialize the muscle
void OpenSim::Millard2012AccelerationMuscle::setFiberCompressiveForceCosPennationCurve ( FiberCompressiveForceCosPennationCurve aFiberCompressiveForceCosPennationCurve)
Parameters
aFiberCompressiveForceCosPennationCurvethe FiberCompressiveForceCosPennationCurve that this muscle model uses to prevent pennation angles from approaching 90 degrees, which is associated with a singularity in this model.
void OpenSim::Millard2012AccelerationMuscle::setFiberCompressiveForceLengthCurve ( FiberCompressiveForceLengthCurve aFiberCompressiveForceLengthCurve)
Parameters
aFiberCompressiveForceLengthCurvethe FiberCompressiveForceLengthCurve that this muscle model uses to ensure the length of the fiber is always greater than a physically realistic lower bound.
void OpenSim::Millard2012AccelerationMuscle::setFiberForceLengthCurve ( FiberForceLengthCurve aFiberForceLengthCurve)
Parameters
aFiberForceLengthCurvethe FiberForceLengthCurve that this muscle model uses to calculate the passive force the muscle fiber generates as the length of the fiber changes
void OpenSim::Millard2012AccelerationMuscle::setFiberLength ( SimTK::State &  s,
double  fiberLength 
) const
Parameters
sthe state of the system
fiberLengththe desired fiber length (m)
void OpenSim::Millard2012AccelerationMuscle::setFiberVelocity ( SimTK::State &  s,
double  fiberVelocity 
) const
Parameters
sthe state of the system
fiberVelocitythe desired fiber velocity (m/s)
void OpenSim::Millard2012AccelerationMuscle::setForceVelocityCurve ( ForceVelocityCurve aForceVelocityCurve)
Parameters
aForceVelocityCurvethe ForceVelocityCurve that this muscle model uses to calculate the derivative of fiber length.
void OpenSim::Millard2012AccelerationMuscle::setMass ( double  mass)
Parameters
massThe size of the mass parameter between the fiber and the tendon. Making this parameter small will make the muscle model more rapidly converge to the results an equilibrium model would produce.

Conditions

    mass >= 0.001
void OpenSim::Millard2012AccelerationMuscle::setPropertiesFromState ( const SimTK::State &  s)
protectedvirtual

Sets the default state for ModelComponent.

Parameters
sthe state of the model

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::setStateVariableDeriv ( const SimTK::State &  s,
const std::string &  aStateName,
double  aValue 
) const
protected

Set the derivative of an actuator state, specified by name.

Parameters
sthe state
aStateNameThe name of the state to set.
aValueThe value to set the state to.
void OpenSim::Millard2012AccelerationMuscle::setTendonForceLengthCurve ( TendonForceLengthCurve aTendonForceLengthCurve)
Parameters
aTendonForceLengthCurvethe TendonForceLengthCurve that this muscle model uses to define the tendon force length curve

The documentation for this class was generated from the following file: